Release highlights:
- BREAKING: dropped support for Python 2 and Python 3.5 ([3232](https://github.com/streamlink/streamlink/pull/3232), [#3269](https://github.com/streamlink/streamlink/pull/3269))
- BREAKING: updated the Python version of the Windows installer to 3.8 ([3330](https://github.com/streamlink/streamlink/pull/3330))
Users of Windows 7 will need their system to be fully upgraded.
- BREAKING: removed all deprecated CLI arguments ([3277](https://github.com/streamlink/streamlink/pull/3277), [#3349](https://github.com/streamlink/streamlink/pull/3349))
- `--http-cookies`, `--http-headers`, `--http-query-params`
- `--no-version-check`
- `--rtmpdump-proxy`
- `--cmdline`, `-c`
- `--errorlog`, `-e`
- `--errorlog-path`
- `--btv-username`, `--btv-password`
- `--crunchyroll-locale`
- `--pixiv-username`, `--pixiv-password`
- `--twitch-oauth-authenticate`, `--twitch-oauth-token`, `--twitch-cookie`
- `--ustvnow-station-code`
- `--youtube-api-key`
- BREAKING: replaced various subtitle muxing CLI arguments with `--mux-subtitles` ([3324](https://github.com/streamlink/streamlink/pull/3324))
- `--funimationnow-mux-subtitles`
- `--pluzz-mux-subtitles`
- `--rtve-mux-subtitles`
- `--svtplay-mux-subtitles`
- `--vimeo-mux-subtitles`
- BREAKING: sideloading faulty plugins will now raise an `Exception` ([3366](https://github.com/streamlink/streamlink/pull/3366))
- BREAKING: changed trace logging timestamp format ([3273](https://github.com/streamlink/streamlink/pull/3273))
- BREAKING/API: removed deprecated `Session` compat options ([3349](https://github.com/streamlink/streamlink/pull/3349))
- BREAKING/API: removed deprecated custom `Logger` and `LogRecord` ([3273](https://github.com/streamlink/streamlink/pull/3273))
- BREAKING/API: removed deprecated parameters from `HLSStream.parse_variant_playlist` ([3347](https://github.com/streamlink/streamlink/pull/3347))
- BREAKING/API: removed `plugin.api.support_plugin` ([3398](https://github.com/streamlink/streamlink/pull/3398))
- Added: new plugin for pluto.tv ([3363](https://github.com/streamlink/streamlink/pull/3363))
- Added: support for HLS master playlist URLs to `--stream-url` / `--json` ([3300](https://github.com/streamlink/streamlink/pull/3300))
- Added: `--ffmpeg-fout` for changing the output format of muxed streams ([2892](https://github.com/streamlink/streamlink/pull/2892))
- Added: `--ffmpeg-copyts` and `--ffmpeg-start-at-zero` ([3404](https://github.com/streamlink/streamlink/pull/3404), [#3413](https://github.com/streamlink/streamlink/pull/3413))
- Added: `--streann-url` for iframe referencing ([3356](https://github.com/streamlink/streamlink/pull/3356))
- Added: `--niconico-timeshift-offset` ([3425](https://github.com/streamlink/streamlink/pull/3425))
- Fixed: duplicate stream names in DASH inputs ([3410](https://github.com/streamlink/streamlink/pull/3410))
- Fixed: youtube live playback ([3268](https://github.com/streamlink/streamlink/pull/3268), [#3372](https://github.com/streamlink/streamlink/pull/3372), [#3428](https://github.com/streamlink/streamlink/pull/3428))
- Fixed: `--twitch-disable-reruns` ([3375](https://github.com/streamlink/streamlink/pull/3375))
- Fixed: various plugins issues (see detailed changelog down below)
- Changed: `{filename}` variable in `--player-args` / `-a` to `{playerinput}` and made both optional ([3313](https://github.com/streamlink/streamlink/pull/3313))
- Changed: and fixed `streamlinkrc` config file in the Windows installer ([3350](https://github.com/streamlink/streamlink/pull/3350))
- Changed: MPV's automated `--title` argument to `--force-media-title` ([3405](https://github.com/streamlink/streamlink/pull/3405))
- Changed: HTML documentation theme to [furo](https://github.com/pradyunsg/furo) ([#3335](https://github.com/streamlink/streamlink/pull/3335))
- Removed: plugins for `skai`, `kingkong`, `ellobo`, `trt`/`trtspor`, `tamago`, `streamme`, `metube`, `cubetv`, `willax`
[Full changelog](https://github.com/streamlink/streamlink/compare/1.7.0...2.0.0)